It is known to provide a mat of resilient material to be used as a base for a bed of broken stones of which the top side is a layer consisting of a material which is different from that of the main material of the mat. Such mats are used to carry, in an elastic manner, the bed of broken stones and the respective lines of rails against the foundation and against tunnel and trough walls in subways and for rail lines in order to effect a damping of rail-traveling sounds.
A mat of the above mentioned type the top side can be provided with a layer of elastically deformable material (DE-GM No. 80 13 779), for instance a bitumen layer. The broken stones can press themselves into this layer to a certain extent so that a more or less non-slip accumulation is achieved. The main disadvantage of this mat is that the sharp-edged broken stones within a short period of time also penetrate into the body of the mat whereby the mat is destroyed in such a way that finally it becomes only a granulated mass. However, a granulated mat is not capable of damping the rail sounds.
The mat can also be provided on its top side with a metal plate (DE-OS No. 31 21 946) which prevents a penetration of the broken stones into the mat. Indeed, this mat guarantees an especially effective damping of impact sound. However, the mat is not very flexible so that it can only be installed in relatively short lengths, a handicap in installation.